This application claims priority of International application number PCT/DE99/03676, filed Nov. 18, 1999, which in turn claims priority to German patent application number 198 55 282.8, filed Nov. 24, 1998.
The invention relates to a two-directional manual drive which produces a rotational movement. A drive of this kind is suitable in particular for manually adjusting the height or rake of a vehicle seat.
A two-directional drive is known from DE 43 09 334 A1 wherein force transfer from a drive lever to a driven shaft takes place through friction locking elements which are mounted on the shaft. When the drive lever is moved away from the neutral position of the drive lever the friction locking elements clamp with the shaft and transfer torque introduced on the drive side to the shaft.
The friction locking elements thus have a friction-conditioned self-locking action when entering into the drive phase with the surface of the shaft which is to be driven. It is thereby ensured that the friction torque is intensified in dependence on the drive torque itself so that large forces can also be transferred. During the reverse movement of the drive lever back towards its neutral position the self-locking action is however lifted and the friction torque is kept as small as possible.
Controlling the conditions of the self-locking action is undertaken by an elastic switching element. Swivel movement of the drive lever beyond its neutral position leads to the expansion of the elastic switching element which is designed in particular as a shaped wire spring. The tangentially acting force which is thereby produced causes tilting and tensioning processes within the scope of the proposed play of the drive device so that the self-locking action can become active and intensified.
In the event of a return of the drive lever to the neutral position the one spring end of the elastic switching element exerts a tangential force on the friction locking elements through a bolt whereby this force acts in the swivel direction of the drive lever and lifts the self-locking properties so that the shaft is prevented from jamming and turning back.
From FR-A 2 750 186 a drive mechanism for producing a rotational movement is known which takes place starting from a neutral position of a drive lever which can pivot about a drive axis selectively in one or other rotational direction. A driven element is only turned when the drive lever is moved away from the neutral position whilst when the drive lever is moved into the neutral position the driven element is not displaced. In order to produce the rotational movement the driven element has internal teeth which interact with two locking pawls mounted on a fixed flange. A toothed segment-shaped disc which is able to swivel about a cam connected to the drive lever with diametric play has two driving pawls of which during activation of the drive lever the driving pawl corresponding to the direction of rotation of the drive lever, as well as the corresponding locking pawl, are brought into engagement with the internal teeth of the driven element whilst the other driving pawl and the locking pawl are kept out of engagement with the internal teeth of the driven element.
The known drive mechanism for producing a rotational movement is automatically locked after each operation of the drive lever so that no additional locking device is required which blocks torque on the driven side but transfers torque on the drive side arising from the drive lever to the device which is to be driven. When the drive lever returns to the neutral position the teeth of the driving pawls are brought out of engagement with the internal teeth of the driven element.
From WO 96 23672 A, a two-directional manual drive is known for producing a rotational movement by means of a drive lever which starting from a neutral position can pivot with restricted angle into one or other rotational direction, through which a shaft is rotated when the drive lever is moved away from its neutral position while the drive lever is pivoted in the direction of the neutral position the shaft is not displaced. The drive lever which is mounted on an axis is provided with swivel detent elements while the ends provided with teeth engage into the teeth arranged round the periphery of a drive wheel. A slide guide is associated with the detent elements and lifts each unloaded detent element out from the teeth of the drive wheel. Furthermore a locking device is connected to the drive shaft so that torque on the output side is blocked while torque on the drive side is transferred.
The object of the present invention is to provide a two-directional manual drive for producing a rotational movement which enables infinite transfer of torque from a drive lever to a driven element, operates without play and noise and which can also be readily used, i.e. without greater demands on tolerance, as a locking clutch with a substantially matching construction with a two-directional drive mechanism and can, therefore, be manufactured cost-effectively.
According to one embodiment of the present invention, a driven element has a cylindrical shaped driving surface arranged concentric with a drive axis and on which bearing surfaces of coupling elements are placed in non-positive fit when the drive lever is rotated out of a neutral position. In this way the driven element is entrained in the direction of the periphery. When the drive lever is returned to the neutral position the coupling elements are released from a position of non-positive fit so that the driven element is no longer displaced as the drive lever is returned into the neutral position.
The solution has the particular advantage that it can be constructed without any spring-elastic switching element. In this way external factors, such as dirt or the like, have substantially little effect or even no effect whatsoever on the functioning of the drive according to the present invention so that proper functioning of the drive according to the present invention is always guaranteed. This also applies in the event of long-lasting and high strain on the drive.
The drive according to the invention preferably has circular section coupling elements which are placed against the cylindrical driving surface through bearing faces of their partially circular shaped surfaces which are opposite the cylindrical shaped driving surface of the driven element. With this embodiment advantageous that the formation of the bearing faces of the coupling elements matches the cylindrical shaped formation of the driving surface so that a particularly good force-locking or frictional engagement connection between the bearing faces of the coupling elements and the cylindrical drive face of the output element becomes possible.
In another preferred embodiment of the drive according to the invention a drive element is mounted between the coupling elements. Furthermore expanding flanks of the coupling elements are arranged at such a distance from the drive axis that a substantially radially aligned force produces the frictional engagement between the coupling elements and the cylindrical driving surface. In the event of the drive lever being moved out from its neutral position, the bearing faces of the coupling elements for transferring torque on the drive side adjoin with a frictional engagement against the cylindrical driving surface of the driven element.
In a further preferred embodiment the bearing faces of the coupling elements adjoin the cylindrical driving surface of the driven element elastically pretensioned by at least one spring element, for example a compression or leaf spring. The spring element thereby preferably bears against the coupling elements in the centre of at least one of the bearing faces and presses these apart from each other in the direction of the periphery until they bear on the drive element with their expanding flanks which are each turned remote from the spring element relative to the drive axis. With this embodiment it is advantageous if the coupling elements bear free of play against both the cylindrical driving surface of the driven element and against the drive element so that a play-free drive becomes available.
In a further preferred embodiment of the present invention, the spring element is placed with positive engagement around at least one angled claw of the drive element and presses the adjoining expanding flanks of the coupling elements apart. For this a W-spring is preferably provided whose ends bear against facing radial end stops of the coupling elements and whose centre section is placed around an angled claw of the drive element. The use of such a spring element ensures a particularly reliable and play-free bearing of the expanding flanks remote from the spring element against the drive element or of the coupling elements against the cylindrical driving surface of the driven element.
In a further preferred embodiment of the present invention, the drive has two coupling elements of identical design arranged symmetrically relative to the drive axis and between which is mounted the drive element which is connected to the drive axis and drive lever. The drive element is thereby formed as a drive vane which, when the drive lever is displaced to transfer torque on the drive side, engages on the facing expanding flanks of the coupling elements so that a substantially radially aligned force produces the frictional engagement between the coupling elements and the cylindrical-shaped driving surface of the driven element. The bearing faces of the coupling elements thus for transferring a torque on the drive side bear against the cylindrical driving surface of the driven element with non-positive fit.
With this embodiment it is advantageous that, as a result of the symmetrical arrangement and the identical design of the coupling elements, the bearing faces of the coupling elements are uniformly distributed around the periphery of the cylindrical driving surface of the driven element so that, when the drive lever is displaced, a particularly good non-positive force-locking connection is produced between the coupling elements and the cylindrical shaped driving surface of the driven element.
With the drive according to the invention a releasing element is preferably provided which has releasing claws which are arranged in recesses of the partially circular-shaped surfaces of the coupling elements opposite the driving surface. Furthermore the releasing element has a spring shackle which is coupled to a restoring spring.
After the drive lever has been displaced from its neutral position the restoring spring and the releasing claws of the releasing element cause the drive lever to return to its neutral position. On letting go the drive lever or operating the drive lever with reduced force no more torque is introduced on the drive side or the torque introduced on the drive side is reduced. As a result of the absence of or reduced radially aligned force the non-positive bearing of the coupling elements against the cylindrical driving surface of the driven element is lifted or reduced.
The restoring spring which is tensioned when the drive lever is turned now acts with its spring force so that the releasing claws of the releasing element press in the direction of the periphery against the stop faces of the recesses of the coupling elements and draw back the coupling elements in the direction of the periphery. The spring force is thereby selected so that the pressing of the free switching claws also overcomes a reduced force-locking connection between the coupling elements and the cylindrical driving face of the driven element.
As a result of the movement of the coupling elements by the releasing claws of the releasing element the drive element which is connected to the drive lever is also entrained along so that the drive lever is also returned to its neutral position. On the other hand the driven element is not drawn back since the force-locking bearing of the coupling elements against the cylindrical drive face of the driven element is lifted or reduced so that torque is not transferred to the driven element.
A coil spring with two ends bearing against a housing stop and against the spring shackle of the releasing element is preferably provided as the restoring spring. Springs of this type have a sufficiently high spring force to return the drive lever to its neutral position. Furthermore springs of this kind can be easily integrated in the structural space directly adjoining the drive lever. In this way the complexity of the drive is increased and space is spared.
In a further embodiment of the invention, the driven element is connected on the driven side to a locking clutch which on the one hand blocks non-positively torque introduced from the driven side of the locking clutch and on the other side transfers to the driven side torque which is introduced on the drive side and is transferred from the driven element to the locking clutch. When using a locking clutch of this kind it is advantageous if no displacement of the drive takes place in the event of external forces, more particularly crash forces.
The locking clutch preferably has a clutch housing with a cylindrical brake surface. Furthermore, brake shoes are mounted in the clutch housing and with a part of their outside faces bear elastically pretensioned against the cylindrical brake surface of the clutch housing. The brake shoes are preferably formed uniform with the coupling elements.
Furthermore, the driven element is connected to a follower wheel of the locking clutch which preferably has cylinder sleeve shaped follower claws which are arranged with torsion angle play with positive fit between two substantially radial stop faces of the brake shoes. The driven side of the locking clutch furthermore has a driven vane arranged between the facing expanding flanks of the brake shoes.
The locking clutch is therefore constructed practically in accordance with the drive described above. Individual component parts, for example, the coupling elements or the brake shoes can therefore be used for both the drive described and for the locking clutch, which reduces the manufacturing costs.
The locking clutch has a different function from the drive described above. Under the action of torque introduced from the driven side of the locking clutch the driven vane presses the outside surfaces of the brake shoes with frictional engagement against the cylindrical brake surface of the clutch housing so that torque transfer is blocked.
In the event of torque transferred from the driven element to the locking clutch no such locking action occurs. Rather the driven element acts with the follower claws so that these press in the direction of the periphery on the radial stop faces of the brake shoes and reduce or lift the force-locking contact of the brake shoes on the cylindrical brake surface so that the follower claws during rotary movement entrain the brake shoes and thus also the driven vane. In this way torque introduced through the drive lever on the drive side is transferred to the driven side.